A Universal Luminosity Function for Radio Supernova Remnants

TL;DR

This study compiles radio supernova remnant data from 19 galaxies to demonstrate a universal power-law luminosity function that scales with star formation rate, unaffected by galaxy ISM density.

Contribution

It provides the first comprehensive analysis showing the SNR luminosity function is universal and correlates with star formation rate, challenging previous assumptions about ISM density dependence.

Findings

SNR populations are similar across different galaxies.

The luminosity function follows a power law proportional to SFR.

No dependence of SNR luminosity on galaxy ISM density.

Abstract

We compile radio supernova remnant (SNR) samples from the literature for 19 nearby galaxies ranging from the SMC to Arp 220, and use this data to constrain the SNR luminosity function (LF) at 20 cm. We find that radio SNR populations are strikingly similar across galaxies. The LF can be described as a power law with constant index and scaling proportional to a galaxy's star formation rate (SFR). Unlike previous authors, we do not find any dependence of SNR luminosity on a galaxy's global ISM density. The observed correlation between the luminosity of a galaxy's brightest SNR and a galaxy's SFR can be completely explained by statistical effects, wherein galaxies with higher SFR more thoroughly sample the high-luminosity end of the SNR LF. The LF is well fit by a model of SNR synchrotron emission which includes diffusive shock acceleration and magnetic field amplification, if we assume that all remnants are undergoing adiabatic expansion, the densities of star-forming regions are similar across galaxies, and the efficiency of CR production is constant.